This invention relates to a magnetic disk device as one of storage devices of computers. More specifically, this invention relates to a magnetic disk device having a positioning structure suitable for reducing the size and the thickness of a magnetic disk device, for achieving a large storage capacity and a high recording density and for improving an information processing speed.
JP-A-8-45205 (hereinafter called the "first related art example") and JP-A-5-325459 (hereinafter called the "second related art example") describe a positioning mechanism for accomplishing the reduction of the size and the thickness of the device, a large capacity, high recording density and a high information processing speed. The first and second related art examples improve positioning accuracy by restraining the vibration occurring in the magnetic disk device.
The first related art example prevents the vibration of a voice coil motor resulting from the movement of a carriage from being transmitted to a base by fixing the voice coil motor and the base through viscoelastic members, or the like.
The second related art example restricts the residual vibration by a spring arm at the time of seek by providing a vibration absorption member to the spring arm.
Because it has been customary to package the magnetic disk device into notebook type personal computers, the reduction of its size and thickness and a large storage capacity and a high recording density of the disk device have been required in the past. Because the notebook type personal computers are mainly of the type which incorporate a battery and can be operated even in the absence of an alternating current outlet, low power consumption is another essential requisite. In addition, reliability and low price of the device and a higher information processing speed are required naturally.
To satisfy these requirements, a positioning mechanism of the magnetic disk device must reduce as much as possible a relative position error between the disk and the head. Factors of the position error include the vibration of the head and a carriage swinging portion for supporting the head and the vibration of the disk and a spindle motor rotation portion for supporting the disk.
If the amplitude of the vibration is great when the head reads out the information recorded circumferentially on the disk surface, the head reads also the information adjacent to the target position in the radial direction. Therefore, the space of the information in the radial direction must be increased. However, a large capacity cannot be achieved in this case, and the reduction of both size and thickness cannot be attained.
The vibration of the head increases the number of times of repetition of correction of the head position in positioning control and requires a long settling time before positioning is made correctly to the target position. Therefore, the vibration of the head also impedes a higher information processing speed of the magnetic disk device.
To use the full surface of the mounted disk, a head arm of a carriage includes a portion at which two heads are mounted via suspensions or spring arms as shown in FIG. 6 and a portion at which one head is mounted via a suspension as shown in FIG. 7. The portion having one head mounted via a suspension thereto involves the problem that the vibration (amplitude) is great.
The systems described in the first and second related art examples have been examined as means for solving the problem but they are not entirely satisfactory for restraining the vibration (amplitude) of the portion at which one head is mounted via a suspension.